Role of M Cells in Human Mucosal Immunity to Mycobacterium tuberculosis

Background

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a bacterial pathogen that infects roughly one-third of the worldÕs population and causes 1–2 million deaths per year. The current paradigm is that phagocytosis of Mtb by patrolling alveolar macrophages initiates Mtb infection. While this model can account for pulmonary TB, it does not adequately explain the occurrence of extrapulmonary forms of TB that manifest in the absence of obvious lung involvement, such as tuberculous cervical lymphadenitis, also known as scrofula. We hypothesized that specialized epithelial cells called microfold cells (M cells) may be an alternate portal of entry for Mtb. Previously we demonstrated that Mtb is able to transcytose across an epithelial barrier in an M cell dependent manner and that M cell mediated transcytosis is vital for Mtb pathogenesis in a mouse model of tuberculosis.

Methods

We used an in vitro M-cell mediated translocation assay and a Mtb mutant lacking a key virulence factor, ESAT6. We used biochemistry and genetics to identify a novel receptor for ESAT6. We also developed a novel explanted human adenoid Mtb infection model to study mucosal immunity.

Results

We now demonstrate that the Mtb virulence factor ESAT6 is necessary and sufficient to mediate binding and transcytosis by M cells in vitro and in vivo, and that uptake of Mtb by M cells requires a unique cell surface ESAT6 receptor. We developed a novel explanted human adenoid model of M cell biology and demonstrate rapid Mtb transcytosis by primary human tissue within 60–120 minutes. Using flow cytometry we find that Mtb is first ingested by M cells and then after transcytosis, by tissue resident antigen-presenting cells. Explanted adenoids from 10 independent donors display a wide range of Mtb uptake.

Conclusion

We conclude that Mtb ESAT6 is necessary for Mtb uptake by M-cells and that binding and transcytosis require a host receptor. Because explanted adenoids display a wide range of Mtb uptake, M cell mediated transcytosis may confer differential susceptibility to scrofula and disseminated disease. These findings are significant as M cells could potentially serve as the basis for novel therapeutic targets against primary Mtb infection.

Disclosures

All authors: No reported disclosures.

Belatacept Conversion in an HIV-Positive Kidney Transplant Recipient With Prolonged Delayed Graft Function

We report an HIV-positive renal transplant recipient with delayed graft function who was converted from tacrolimus to belatacept in an attempt to improve renal function. The patient had kidney biopsies at 4 and 8 weeks posttransplant that revealed acute tubular necrosis and mild fibrosis. After 14 weeks of delayed function, belatacept was initiated and tacrolimus was weaned off. Shortly after discontinuing tacrolimus, renal function began to improve. The patient was able to discontinue dialysis 21 weeks posttransplant. HIV viral load was undetectable at last follow-up. To our knowledge, this is the first report of belatacept use in a patient with HIV.

Fatal coronary sinus thrombosis due to hypercoagulability in Crohn's disease

A 27-year-old male, admitted to hospital for a psoas muscle abscess secondary to Crohn's disease, suddenly died while in hospital. A medicolegal autopsy showed coronary sinus thrombosis. Coronary sinus thrombosis is rare and is usually associated with invasive cardiac procedures. Coronary sinus thrombosis associated with Crohn's disease has not been reported. Autopsy examination of the coronary sinus is advocated, especially in individuals with hypercoagulable states.

Chronobiologic Considerations in Pharmacologic and Toxicologic Studies: Fact or Fancy

Previous studies showing circadian variation in pharmacologic response to drugs in man and experimental animals have been reviewed. The chronobiologic response is discussed in terms of the pharmacologic factors that determine drug action. The importance of internal markers in chronopharmacologic studies is emphasized and is illustrated by our studies with the antihypersive drugs. Identification of chronobiologic variations in the therapeutic and toxic response to drugs, when present, along with an understanding of their mechanisms, would permit the design of optimal therapeutic regimens for these drugs.

Cryopreservation of specialized chicken lines using cultured primordial germ cells

Biosecurity and sustainability in poultry production requires reliable germplasm conservation. Germplasm conservation in poultry is more challenging in comparison to other livestock species. Embryo cryopreservation is not feasible for egg-laying animals, and chicken semen conservation has variable success for different chicken breeds. A potential solution is the cryopreservation of the committed diploid stem cell precursors to the gametes, the primordial germ cells ( PGCS: ). Primordial germ cells are the lineage-restricted cells found at early embryonic stages in birds and form the sperm and eggs. We demonstrate here, using flocks of partially inbred, lower-fertility, major histocompatibility complex- ( MHC-: ) restricted lines of chicken, that we can easily derive and cryopreserve a sufficient number of independent lines of male and female PGCs that would be sufficient to reconstitute a poultry breed. We demonstrate that germ-line transmission can be attained from these PGCs using a commercial layer line of chickens as a surrogate host. This research is a major step in developing and demonstrating that cryopreserved PGCs could be used for the biobanking of specialized flocks of birds used in research settings. The prospective application of this technology to poultry production will further increase sustainability to meet current and future production needs.

Sudden cardiac death due to coronary artery dissection as a complication of cardiac sarcoidosis

Spontaneous coronary artery dissection (SCAD) is a rare cause of acute coronary syndrome (ACS), cardiac tamponade and sudden cardiac death that typically affects young women in the postpartum period. Rarely, it can be caused by systemic inflammatory conditions such as sarcoidosis. Sarcoidosis is an inflammatory disease most often affecting the lung and lymph nodes that can sometimes affect the heart. The authors report a case of sudden cardiac death caused by SCAD in the context of undiagnosed and subclinical cardiac sarcoidosis. The decedent was a 47-year-old male with a relatively innocuous past medical history. He was found dead in bed. At autopsy, there was a lethal hemopericardium resulting in cardiac tamponade. Gross examination of the heart revealed dissection of the posterior descending coronary branch of the right coronary artery. Histologically, the coronary artery showed acute and organizing dissection with evidence of vasculitis. A chronic inflammatory infiltrate consisting of lymphocytes, histiocytes, eosinophils and giant cells was seen. Sections of the myocardium showed myocarditis with a nonnecrotizing granuloma. The death was attributed to cardiac tamponade secondary to SCAD in the context of systemic sarcoidosis. The presented case demonstrates two concurrent rare pathologies and highlights the importance of considering SCAD in cases of sudden cardiac death at autopsy.

Evading Detection and Antibiotics: Internalization Rates of Different Strains of Group A Streptococcus

Objectives:

(1) Determine the internalization rates of different strains of Group A Streptococcus (GAS). (2) Determine whether statistically different internalization rates occur in patients who receive a tonsillectomy for sleep-disordered breathing/sleep apnea versus chronic/recurrent tonsillitis. (3) Facilitate the development of GAS vaccine

Methods:

In vitro microbiology/tissue culture study at an academic tertiary referral center. All tonsillectomy specimens (performed for sleep disordered breathing spectrum and recurrent/chronic tonsillitis spectrum) were collected at the authors’ institution from September 2013 to November 2013. Each specimen was swabbed and bacteria cultured and emm typed. Only specimens with GAS were included in the study. The strains were grown in brain heart infusion (BHI) media to an optic density at 600 nm of 0.5. HeLa and nasopharyngeal carcinoma Detroit 562 cells were grown in tissue culture and subsequently infected with individual strains of GAS at a multiplicity of infection (MOI) of 1:10 for 2 hours. Cells were then washed with Dulbecco’s Modified Eagle Media (DMEM) and reincubated with DMEM plus gentamycin. The cells were then lysed, serial dilutions performed, and the lysate plated. Bacteria were counted and percent internalizations were calculated. This was repeated in triplicate for each strain.

Results:

Out of 396 eligible patients, 66 strains of GAS have been isolated. Both the Detroit and HeLa cells have been successfully grown in BHI. The bacterial strains have been subcultured. The authors plan on infecting the cells in March 2014 and will have have conclusive results by April 2014.

Conclusions:

None provided.

Femoral artery pseudoaneurysm due to Candida albicans in an injection drug user

Candida arteritis is an uncommon condition but important to recognize due to the risk of significant morbidity and the difficulty in management of the enduring fungal infection. The authors report a rare case of a man with a femoral artery pseudoaneurysm with persistent Candida albicans infection, as a complication of infective endocarditis. The 23-year-old man, with a history of chronic intravenous drug use and Type I diabetes mellitus, presented with left groin pain, paresthesia of his left foot, and a pulsatile mass in the inguinal region. On imaging, he was found to have a pseudoaneurysm of the left common femoral artery, which later ruptured. Further investigation revealed vegetations on the mitral and aortic valves as well. Initial blood cultures were negative. He underwent multiple surgical interventions including replacement of the mitral and aortic valves and resection of the left common femoral artery with autogenous revascularization. In addition, he was commenced on intravenous antifungal therapy. Postoperatively, he continued to experience significant pain in the left groin and had two episodes of rerupture of the femoral artery that was consequently surgically repaired. Histological examination of the resected valves revealed vegetations with a mixture of fungal elements and bacterial cocci. The femoral artery resection specimens revealed evidence of infectious arteritis and the presence and persistence of C. albicans organisms in subsequent specimens. This case highlights the importance of an accurate diagnosis and aggressive management of fungal mycotic aneurysms in at-risk populations.